Explanation:
The stars
beyond
the Sun and the distant galaxies should be undetectable at extreme
ultraviolet
wavelengths.
At least that was the conventional wisdom when it was first
realized that the space between the stars is
filled with hydrogen,
a strong absorber of extreme ultraviolet light.
But this idea was seriously questioned as it became apparent
that interstellar hydrogen was patchy
in its distribution and
the quest to explore
the extreme ultraviolet sky culminated
in 1992 with the launch of
the EUVE
(Extreme UltraViolet Explorer) spacecraft.
An all-sky map,
based on
the satellite's first six months of operation, appears above
showing brightness variations in
the EUV sky
in false colour (north is up).
EUVE's scanning by orbit
gives
the picture a striped look
while other instrument artifacts are seen as crosses and
data gaps are dark.
Multiple images of the Moon
combine to form the short, bright dashed lines
wandering along the middle of the picture.
The belt stars of the familiar constellation
Orion are
fairly easy to make out left of picture centre.
EUVE's science operations ceased in 2001 but it
ultimately
detected nearly 1,000 celestial objects, including over three dozen
outside our own galaxy.
EUVE's voyage
of
discovery is now complete, and
the spacecraft
re-entered the Earth's atmosphere yesterday
at approximately 11:15 p.m. EST.